Appendix VI. 1091 The product of polar distance by intercept is an easier method of finding a moment, because the former can be fixed artificially as 10, or some simple multiple thereof. This proof will also serve for the Culmann bending moment diagram, pp. 446 and 885. Problem. To draw a link polygon which shall pass through three given points in the space diagram. As the practical application is to cases of vertical and parallel forces, such case only will be here considered. Re- ferring to Fig. 964: let A B c be the given points, and D, E, F, G, and H the given forces. The latter are set down in magnitude and direction as o i, 12, 2 3, 3 4, and 4 5 on the vector figure. 1. Firstly, make no attempt to pass through the points, but choose any pole d and draw the polygon hfg. 2. Take the two links Oi and 03 immediately over A and B and produce them to find the resultant a b. The same pair of links in any other polygon would have the same resultant, for the pole can be chosen anywhere. 3. Take any point d, join to A and B and produce, forming two such links in a new polygon.